There are a variety of medical procedures that would benefit from the availability of new materials that can be introduced into the body of a mammal for purposes such as tissue bulking, filling voids, forming occlusions, absorbing fluids, and delivering medications. Tissue bulking includes introduction of materials in a collapsed area to provide a filling function, for example in cases where the natural tissue has degenerated such that control of a normal function has deteriorated. Esophageal sphincter and urinary tract control are examples. Void filling involves introduction of materials into an empty space, such as one created by removal of a tissue mass. Void filling may also be used when a tissue cavity is malfunctioning. Occlusions may be imposed to block ducts as well as vasculature. Absorbing fluids and delivering medications is useful in wound treatment, including those caused surgically and accidentally, and involves introduction of materials to stop bleeding, provide padding, deliver medication, and absorb fluids. Such materials are useful especially in emergency situations including accidents and military operations.
Hydrogel microspheres have been used in some of these medical applications. Characteristics of the medical treatment are generally related to the properties of the specific type of hydrogel microspheres used in the treatment. The properties of the hydrogel microspheres are in turn generally dependent upon the materials used in microsphere preparation and the process by which the microspheres were prepared.
U.S. Pat. No. 6,218,440 discloses a process for preparing hydrogel microspheres which produces microspheres that have many cavities joined by interconnecting pores, with cavities at the interior of the material in communication with the surface. In the process disclosed therein, an emulsion is first prepared, and then this emulsion is suspended in an oil medium. The resulting microspheres have high absorption capacity and are said to be useful for adsorption of fluids or chemicals.
U.S. Pat. No. 4,446,261 discloses a process for making hydrogel microspheres which includes dispersing a solution containing monomer, crosslinking agent and initiator in a dispersion medium consisting of hydrocarbons having from 6 to 10 carbon atoms or halogenated aromatic hydrocarbons, with a protective colloid dissolved in this oil material.
U.S. Pat. No. 6,436,424 discloses microspheres suitable for dermal augmentation that are said to swell upon contacting physiological fluids at the injection site to up to four times the average diameter of the microspheres prior to injection. These hydrogel microspheres are said to be made by standard methods of polymerization and microsphere preparation described in the art. The microspheres described in U.S. Pat. No. 6,790,456 are the same as those described in U.S. Pat. No. 6,436,424.
WO 2001072281 discloses hydrogel microspheres as described in U.S. Pat. No. 6,436,424 and U.S. Pat. No. 6,790,456 that are associated with bioactive therapeutic factors such as drugs, genes and diagnostic agents, for use in embolization.
JP1994056676A discloses a suspension used for embolization containing lipidic contrast agent and highly water absorbant hydrogel particles of vinyl alcohol and sodium acrylate polymer that are approximately 1.0 mm in diameter or less.
There remains a need for methods of medical treatment where microspheres with outstanding properties, including high swelling and deformability, are administered to provide effectual tissue bulking, void filling, occlusion forming, fluid absorbing, and medication delivering treatments.